1. Field of the Invention
The present invention relates to a synchronous machine control apparatus provided with an electric-power conversion unit that drives a synchronous machine.
2. Description of the Related Art
As is well known, in the case where a synchronous machine having a permanent magnet, as a magnet-field magnet, is controlled by a synchronous machine control apparatus having an electric-power conversion unit such as an inverter, a temperature rise due to energization of the armature of a synchronous machine or the like causes a so-called “demagnetization” phenomenon in which the intensity of magnetization of the magnetic-field permanent magnet, i.e., the magnetic flux is reduced; furthermore, when the allowable temperature is exceeded, a so-called “irreversible demagnetization” phenomenon is caused in which even when the temperature falls down to the normal temperature, the magnetic flux does not return to the state at a time before the demagnetization is caused.
Accordingly, it is required that when a synchronous machine having a permanent magnet as a magnetic-field magnet is controlled, at least the temperature of the permanent magnet is suppressed at a temperature lower than the allowable temperature at which irreversible demagnetization is caused. However, due to a space problem caused by the structure of the synchronous machine, a case protecting the outside of the synchronous machine, or the like, it is difficult to directly mount a temperature detection device on the permanent magnet; furthermore, most of synchronous machines having a permanent magnet as a magnetic-field magnet include the permanent magnet at a position that is inside the permanent magnet and in the vicinity of the rotor, resulting in a further large obstacle factor against mounting the temperature detection device. Accordingly, there is required a technology for indirectly measuring or estimating, with some sort of method, the temperature of the permanent magnet or the magnetic flux related to the temperature of the permanent magnet.
As an example of synchronous machine control apparatus that solves these problems, there exists a conventional apparatus (for example, refer to Patent Document 1) in which based on information items about the current, the temperature, and the rotation speed obtained from a current sensor that detects the current to be exchanged between the inverter and the armature winding, a temperature sensor that detects the temperature of the armature winding so as to correct the resistance value of the armature winding, and a magnetic pole position sensor that detects the magnetic pole position of the magnetic-field magnet, respectively, the value of the magnetic flux that departs from the magnetic-field permanent magnet and is interlinked with the armature winding is obtained by a magnetic flux observer consisting of a model of the synchronous machine (electric rotating machine) and a proportion integrator.
As another example of similar control apparatus, there exists a conventional apparatus (for example, refer to Patent Document 2) having a magnet temperature estimation unit in which when the armature winding (stator winding) is energized, map data corresponding to a battery inter-terminal voltage outputted from a voltage detector is firstly selected from respective map data items for two or more power source voltages stored in a reference magnetic-field current map, map data items corresponding to the torque detected by a torque sensor, the rotation speed outputted from an angle calculation unit, and the q-axis current (that denotes a magnetic-field current in the present invention, described later), among the respective map data items for two or more predetermined reference magnet temperatures included in the selected map data, are selected, and then the predetermined reference magnet temperature corresponding to the selected map data items is set as a magnet temperature estimation value.
As another example of similar control apparatus, there exists a conventional apparatus (for example, refer to Patent Document 3) in which based on the rotation speed of a synchronous machine, the basic wave current or the command value therefor, and the harmonic voltage command value having a frequency that is integral multiples as high as the basic wave frequency, the magnetic flux that is generated by the permanent magnet of the synchronous machine and is interlinked with the armature (armature-interlinked magnetic flux) is calculated, and with reference to a table for the permanent-magnet temperature vs. the armature-interlinked magnetic flux, the permanent-magnet temperature for the calculated value of the armature-interlinked magnetic flux is estimated.
Furthermore, as another example of similar control apparatus, there exists a conventional apparatus (for example, refer to Patent Document 4) having a voltage detector that detects the input voltage to a permanent-magnet-type synchronous motor, a voltage component converter that extracts the q-axis voltage from the output of the voltage detector, a rotation speed detector that detects the rotation speed, and a temperature estimation device that sets and stores the primary resistance of the permanent-magnet-type synchronous motor in a setting storage unit and that estimates a temperature change in the permanent-magnet-type synchronous motor, based on the d-axis current, the q-axis current, the q-axis voltage, the rotation speed, the primary resistance in the setting storage unit, and the magnetic flux.
Each of Patent Documents 5 and 6 discloses an example of technology in which based on a voltage command for a synchronous machine and an armature current, the rotation position of the synchronous machine is estimated through a calculation.